410 



Arthur and Kern : Peridermium 



Pycnia hemispherical, on leaves. 



Mycelium perennial ; aeeiospores small. 

 Peridia cylindrical. 

 Peridia flattened laterally. 



Mycelium annual. 



Peridia cylindrical. 

 Peridia flattened laterally. 

 Pycnia conoidal, on stems. 

 Mycelium perennial. 



26. P. Peckii. 



27. P. elatinum 



28. P. bahameitm 



29. P. Laricis. 



30. P. Ephedrae. 



Pinus : 



Host key 



Foliicolous. 



Peridia very low and fragile. 



Spores thin-walled. 

 Peridia medium high (0.5-0.8 mm. ). 



{ species undet. } 



Spores thin-walled. 



Spores thick-walled. 

 Peridia high and firm (0.7-1.8 



mm. ). 

 Spores thick-walled, moder- 



ately verrucose. 

 Peridial cells medium, 



P. Murray ana 

 P. scopuloritm 

 { P. rigid a \ 



walls equally thick. { P. echinata } 



Spores thick- walled, coarsely 



verrucose. 



P. Taeda 

 P. pa lust r is 

 P. Elliuttii 



Caulicolous. 



Peridial cells very large, 

 walls thick. 



Peridial cells medium, 



walls equally thick. { P. rigida } 

 Peridial cells medium, 



outer wall thinner. { P. fihfolia} 



Branch slightly or not swollen. 

 Peridia cylindrical. 

 Peridia hemispherical. 



{ P. ponderosa } 



Spores moderately ver- (P. Murrayana 



rucose. 



Spores coarsely verru- 



P. Jeffreyi 

 P. 



rigida 



cose. 



Branch gradually swollen into a 



gall. 



Peridia hemispherical or tor- 

 tuous. 



P. sylvestris 

 P. virginiana 



P. 



tnsignis 



Spores finely verrucose. 



P. Murrayana 

 P. pander os a 

 P. contorta 



I. P. delicatulum 



2. P. montanum. 



3. P. acicolum. 



5. P. intermedium. 



4. P. carneum. 



6. P. Rostrupi 



7 



P. gracile. 



8. P. Jila7nentosum 



9. P. stalactifonne 



IO. P. pyriforme. 



II. P. Harknessii. 



